1. Field of the Invention
The present invention is directed to a method for data transmission in a ring network and to a system suitable therefor. More specifically, the present invention is directed to a method for data transmission in a 2-fiber ring network with a plurality of network nodes wherein working signals are bidirectionally transmitted between terminal multiplexers and add-drop multiplexers on the ring network and wherein protection signals are bidirectionally transmitted over other parts of the ring network.
2. Description of the Prior Art
The report of the ICC '93 IEEE, 2/1993, pages 1245 through 1251 reveals optical communication networks with different ring structures that employ wavelength-division multiplex methods in signal transmission. Patent applications DE 43 37 089 A1, E 0651529 and E 0651528 A1 disclose optical ring networks wherein signal transmission occurs in a wavelength-division multiplex mode, whereby signals allocated to individual, specific wavelengths can be coupled out and coupled in. In a way which is known, these ring networks can be equipped with a monitoring ring in addition to what is referred to as a working ring.
The contribution "First results of an experimental Coloured Section Ring" in '22 European Conference on Optical Communication--ECOC-96", Oslo, WeB.2.3, page 3.51 to page 3.54 reports about a ring structure that is shown in FIG. 1. Such structure bidirectionally connects add/drop multiplexers, which neighbor one another, to one another via two light waveguides--one light waveguide being provided for each transmission direction. Only a single wavelength is used for the transmission between two add/drop multiplexers, whereas, however, different wavelengths are used on all other transmission sections.
The infeed and outfeed of signals occurs via optical add/drop multiplexers (OADMs) that correspond to optical filters (FIGS. 3, 4 and 5). This structure was tested for SDH connections (Synchronous Digital Hierarchy). Modern data networks should both enable point-to-point connections of terminal multiplexers and enable the operation of add/drop multiplexers which are connected to one another in a ring-like fashion. An alternate circuit is absolutely required. Further, optimally short switchover times should be achieved in case of malfunction.